Rolf Harris's lawyer has accused an alleged victim of the Australian entertainer of fabricating childhood sexual abuse to cover up a later consensual affair.

The 49-year-old woman said Harris first abused her as a 13-year-old girl and regularly assaulted her for the next 16 years.

But Harris's defence counsel Sonia Woodley said there had been "sexual chemistry" and a consensual relationship which began when she was 18.

"You tried to absolve yourself of blame and say Rolf Harris had abused you, when in fact you had a consensual relationship," she said.

"Once you had told that story you had to stick with it."

A global star of family TV entertainment for more than 50 years, Harris, 84, is on trial charged with 12 counts of indecent assault against four girls between 1968 and 1986, the youngest of whom was aged just seven or eight at the time of the alleged offence.

Harris denies all the charges.

Ms Woodley said that the woman had flirted with Harris and had had an adult relationship with the entertainer.

Referring to an alleged incident at the Harris family home in Berkshire, southern England, she said: "Once again there was a sexual chemistry between the two of you ... one thing led to another."

"You have said this happened when you were much younger and not consenting," she added.

"In fact it happened when you were older and were consenting."

The woman said that after 16 years of abuse she was drinking heavily and unable to refuse Harris and that all subsequent sexual activity was without her consent.

She added: "I didn't really have any resistance ... I was in an alcohol-induced state whenever he was around. I just went along with it because I was scared of him."

Alcoholism sparked by abuse: witness

The court has previously heard that the woman began drinking heavily as a teenager and was an alcoholic for much of her adult life.

Ms Woodley said that as an adult she had needed an excuse to explain her drinking to her parents.

"Rather than blame yourself, you decided to put the blame on Rolf Harris and say that he had turned you into an alcoholic," she said.

"He had," the woman replied.

Prosecutor Sasha Wass asked: "What upset you mother more? The fact that you were an alcoholic or that you had been abused from the age of 13?"

The witness replied: "That I had been abused. Then it all made sense why I was an alcoholic. I loathed myself ... I felt I could have stopped it and I should have stopped it."

Harris was accused of first assaulting the woman as a 13-year-old, when she was getting out of the shower on holiday.

But during this holiday, on the day Harris allegedly groped her on a beach within yards of his sunbathing wife and daughter, she wrote "today was great" in a diary she had been keeping, the jury of six men and six woman was told.

"There is no mention in that diary, or even a hint, of anything unpleasant happening to you at the hands of Rolf Harris is there," said Ms Woodley.

"I wouldn't have put it in a diary," she replied. "If someone saw my diary, I wouldn't want them to think I'd had an awful time."